Tweezers

ABSTRACT

The invention relates to tweezers made of light weight metal ( 10 ) and having two pincers ( 12, 14 ) each of which forms a head part ( 13 ) on one of their ends and can be reversibly and temporarily brought together on their other end by manually applying a closing pressure; the tweezers ( 10 ) preferably consist of extruded light weight metal and are embodied as a single pierce. A closed novel extrusion profile ( 60 ) with an approximately tweezers-shaped cross-section is preferably used in the production of the tweezers.

This is a National Phase patent application based on PCT/CH00/00441filed 18 Aug. 2000 which in turn is based on EP Application No.99810749.4 filed 20 Aug. 1999, the priority being claimed.

BACKGROUND OF THE INVENTION

The invention concerns a pincette which, in a manner known per se, hastwo legs connected at one of their ends with each other, and which endscan be brought in temporary engagement with each other at their otherends by impact of a manually effected closure pressure.

Pincettes of this type have been known for a long time and in manyembodiments, such as disclosed, for example, in DE GM 85 31 382, CH 376064, and EP 0 849 048. Essentially, such pincettes consist of two legs,generally made of steel, interconnected at one of their ends by welding,soldering, or riveting.

As described in DE 28 22 706 in more detail, the force required to closethe pincette, i.e. the minimal manual closure pressure, must besufficient to assure a good gripping of the pincette but must not be sohigh that operation leads to fatigue. In other words, the pincette mustbe neither too “soft” nor too “hard”. In order to replace conventionalforged and, thus, expensive pincettes by disposable pincettes, asdisclosed in the entire document just mentioned, the pincette proposedtherein is made of thin sheet-metal from which profiled pincette legsare formed and connected, e.g. by spot welding. This indicates that thefine sheet-metal must consist of a material, such as steel, which iscapable of being processed in this manner.

For reasons of weight and costs it would be desirable that suchpincettes would consist of a light-metal yet have the essentialmechanical properties of known forged pincettes and could be produced ina simple and economic manner.

Therefore, a first object of the invention is to provide a pincette madeof a light-metal having the same essential mechanical properties asforged pincettes. A second object is to provide a method for economicalmanufacture of such light-metal pincettes.

U.S. Pat. No. 5,192,106 discloses tongs made of spring-steel, plastics,aluminum, copper, brass, or a composite material for handling compactdisks (CDs) capable of gripping a CD both at its outer edge as well asat the edge of a central opening. For both types of function, the legswill not be closed as it would be the case with a pincette. Tongs ofthis type, by necessity, differ from pincettes, both with regard tomechanical properties as well as to shape.

DE 198 11 033 discloses a multi-component tubular shaft-tongs tool forsurgical purposes wherein the pull- and push-rods, the operatinghandles, the shaft and the jaw-type working tool consist of aluminum oraluminum-alloy and are coated with aluminum nitride.

To the best of the applicant's knowledge, the state of the art does notcomprise a teaching indicating in which manner a usable light-metalpincette, i.e. one having the essential mechanical properties, should bemade-up, or how it could be manufactured in an economical manner.

Applicant's research leading to the present invention has shown thatthis aim cannot be achieved by a simple exchange of material because theconnection of pincette legs made of a light-metal by riveting, welding,or gluing is problematic, yields an unsightly connecting site, requiresexpensive processing (inert-gas welding), or will not have sufficientstrength, nor be sufficiently temperature-resistant, respectively.

Also, the “monolithic” structure of pincettes made of steel disclosed inDE 295 12 216 by bending deformation is not suitable for pincettes madeof a light-metal because of the characteristics of these materials, andthe structure is not monolithic because of the milled-in spring element.

The invention, in a first embodiment, concerns a pincette of the typedefined in the introductory paragraph, i.e. having two legsinterconnected at one of their ends and capable of being brought intotemporary and reversible contact at the other end by impact of a manualclosure pressure, and is characterized in that the pincette essentiallyconsists of a preferably extruded light-metal and is structuredmonolithically.

The term “monolithic” used here in the context of pincettes indicatesthat the light-metal of both legs is entirely homogenous even in theircommon apex area, that is, being connected neither mechanically nor bywelding, much less by soldering or gluing. In other words, the pincetteaccording to the invention consists of one integral work piece (i.e.unlike forged pincettes of two interconnected pieces) and normally doesnot have additional functional members. Thus, use of additional springelements is to be excluded, notably since the resilient elasticity of apincette according to the invention is quite sufficient per se.

“Essentially consisting of a light-metal” indicates herein that allessential parts of the pincette consist of a light-metal. Nevertheless,this does not preclude use of a coating varnish, decorations, plasticcoatings or laminates, e.g. for electric insulation or the like.

It was found that the closure pressure of a pincette according to theinvention should, in general, be at least about 120 g, preferably atleast about 150 g, and typically at least about 200 g. For reasons ofsimplicity, the closure pressure indicates the minimum manual pressurethat has to be applied to a pincette, in its state at rest, just forachieving mutual contact of the “lower” or “distal” ends but without anyadditional pressure for grasping an object. The “upper” or “proximal”end of the legs herein refers to the apex area forming the transition oflegs while the “lower” or “distal” end of the legs refers to theopposite end. The closure pressure is also an indication of theresilient elasticity, or resilient capacity, of the legs of thepincette, and should not, under normal conditions and upon anessentially indefinite period of use, change significantly.

The qualification of numeric values by “about”, here and below, isintended to refer to an admissible deviation by ±15% from the statedvalue.

The closure pressure can be measured in a rather simple manner with anaccuracy sufficient for the invention, e.g. on a letter-balance byobserving the difference value between the dead weight of the pincetteand the weight indicated when the distal ends of the legs of thepincette just get into contact with each other.

When normally, i.e. manually, actuating a pincette, the manually exertedpressure for grasping an object usually is a multiple of the closurepressure. Consequently, it is essential for normal functioning of apincette according to the invention that it will not be deformedpermanently by any normally effected manual pressure, i.e. without theuse of tools.

Quantitatively expressed, this means that no permanent deformation ofthe pincette will be observed at a manual pressure that is a multiple oftypically at least 10-times the closure pressure.

It was found that both the closure pressure as well as the maximumpressure, that does not result in a permanent deformation, of pincettesmade of a light-metal or a light-metal alloy according to the inventioncan be controlled by a relatively small local increase of thickness ofthe material.

This would require a considerable technological effort which—accordingto a second object of the invention—can be avoided by using the methodaccording to the invention.

This method for producing a monolithic light-metal pincette constitutesa further embodiment of the invention and is characterized by providingan extruded light-metal profile having a cross-sectional shape whichapproaches that of the pincette to be produced, and dividing into piecesthe profile at least approximately transverse to its longitudinal (oraxial) direction to obtain a plurality of pincettes or “green”pincettes, respectively.

The definition “at least approximately transverse to the longitudinalextension” is intended to include a deviation of up to 15 degrees(corresponding to a cutting angle of up to 75 degrees, or a deviation of⅙, respectively).

According to a preferred embodiment, a closed profile is used to thisend. It can be divided slantwise at its lower end prior or subsequent todivision into pieces so as to form claws.

An extruded light-metal profile, having the shape at least approachingthe shape of a pincette, constitutes another embodiment of theinvention. Preferably, such a profile is provided as a closed profile,i.e. it defines, in a radial direction, a closed space. “Radial”, inthis context, indicates a direction perpendicular to the axial orlongitudinal direction (e.g. the direction of pressure-extrusion of theprofile) of the extruded profile. In contrast, the longitudinaldirection of a pincette according to the invention extends from itsupper to its lower end.

The term “extruded profile” is understood to designate a semi-finishedproduct having a defined cross-sectional profile and any desired length,as it can be obtained by extrusion under pressure or tension. Theextruded profile according to the invention consists essentially of alight-metal composition known, or expected to be suitable, forproduction of extruded profiles by those experienced in the art.

It is to be noted, that use of an extruded profile material as asemi-finished product for production of pincettes according to theinvention is preferred primarily for economic reasons; as a matterprinciple, both an individual production of a pincette according to theinvention, as well as production of extruded profile materials by othermeans than extrusion under pressure or tension appear possible.

Thanks to the properties of light-metals, such profiles according to theinvention can be made by various shaping techniques, such as by drawingor pressing. As a matter of principle—yet under normally prohibitiveproduction costs—light-metal pincettes according to the invention couldalso be produced individually, e.g. by molding, forging, or othertechniques for individual production so that manufacture fromlight-metal profiles is preferred for economic reasons, but is notabsolutely critical from a functional point of view, as long as theproperties of the metal structure obtained are consistent with those ofa profile shaped by extrusion under pressure or tension.

Achieving a solution of the aim of the invention, namely to providelight-metal pincettes having most advantageous properties, and to find atechnologically favorable method of producing such pincettes, wassurprising and was not, in any way, obvious from prior art.

Production of pincettes according to the invention can be simplified ina nearly dramatic manner. While, prior to the invention, production ofpincettes with the essential properties of forged pincettes needednumerous production steps so as to substantially preclude automatedproduction methods, production is reduced to providing a singlesemi-finished product, i.e. the extruded profile according to theinvention, and division thereof into a plurality of pincettes. Bothsteps can be achieved in a completely automated manner when using aclosed profile material, as will be explained in detail below.

However, this does not preclude a finishing step, e.g. for producingspecific shapes at the lower ends of the legs and/or for surfacefinishing by mechanical, physical, or chemical, includingelectrochemical, processes.

As mentioned briefly above, pincettes according to the invention,according to a preferred embodiment for the control of essentialmechanical properties of the pincette (i.e. a sufficiently high closurepressure and a high resistance against permanent deformation), have anincreased gauge or bulge in the apex area and/or near the lower ends ofthe legs.

In this context, “bulge” is understood to refer to a local increase ofnormal thickness of the pincette legs. Typically, such bulges have athickness which is greater at least by 20% than the normal thickness ofthe legs. “Normal” thickness of the legs, in other words, is thereferenced thickness in the predominant part of the legs between thepincette points (working end) and the pincette end (connection of thelegs). As a rule, the bulge of the legs is limited to a maximum of abouta third (33%) of the whole pincette length, and is near the end of thepincette.

The legs of a pincette according to the invention can be shaped, attheir lower ends which can be brought into mutual contact, in a mannerknown per se, as claws and/or pointed ends. Generally, the cross-sectionof the legs between their ends has a prismatic and, preferably, anessentially rectangular shape, the height of which corresponds to thenormal thickness of the legs while the width thereof is at least twiceas great as the normal thickness.

As already mentioned briefly, the apex area according to a preferredembodiment, has a thickness increased by at least about 20%, and isfrequently provided on the inner side as a rounded surface. As explainedbelow, this is not critical, if the grain structure, especiallycrystallinity, of the light-metal used insures a sufficient closurepressure, even without a bulge. Frequently, an optional bulge of thelegs is positioned at the lowest third of the legs, i.e. near thegripping ends in the region of the pressure impact resulting from normalmanual operation. According to a preferred embodiment, a bulge of thelegs is dimensioned such that—upon impact of a manual pressure thatcould lead to permanent deformation—they will contact each other. Inthis manner, resistance against deformation can be increased into anarea of forces well beyond those that could be achieved manually andwould cause cold deformation of the light-metal.

Preferred but not limiting embodiments of pincettes according to theinvention will now be explained by way of the drawings, in which

FIG. 1 is a side view of a pincette according to the invention, or of alight-metal profile from which it is produced, respectively, and

FIGS. 2–5 are fragmented representations of some examples ofmodifications of the apex area of pincettes according to the invention,and

FIG. 6 is an example of a preferred extruded profile according to theinvention.

Specifically, FIG. 1 shows a semi-diagrammatic side view of pincette 10and of the light-metal profile, respectively, from which the pincettehas been produced by cutting or dividing, respectively, the profile, atleast substantially vertical to the longitudinal extension of theprofile, to form a sequence of profile pieces, preferably all havingsubstantially the same width.

Legs 12, 14 extend from their ends 121, 141, shaped in the manner ofclaws, to apex area 13, where they are connected integrally andcontinuously. Apex area 13 can be shaped as a bulge in that itsthickness at a cross-section along the longitudinal axis of pincette 10through apex S is at least 20% greater than the thickness of legs 12, 14in apex 13 at their transition. According to a preferred embodiment, theinner face of apex area 13 indicated as 130 is shaped as an arch orsemi-circular shape, respectively. The shape of the outer face can besimilar or different as long as the apex, in apex area 13, has asufficient thickness. It is to be understood that ends 121, 141 can haveany other required shape, e.g. forming slanted, pointed or point-slantedends, but this aspect is not considered essential for the invention.

Near their claw-shaped ends 121, 141, or near apex area 13, legs 12,14can be provided with bulges 171, 172 and 151, 152, respectively, so asto limit deformation of pincette 10 upon impact of an excessive manualclosure pressure and achieving a practically unlimited resistanceagainst permanent deformation.

Legs 22, 24, according to FIG. 2, continue monolithically from one intothe other in apex area 23 forming an acute angle at apex S while innersurface I is arch-shaped or substantially semi-circular. This, again, isa preferred but not a critical condition because a pincette according tothe invention could also be shaped as shown in FIG. 3 where legs 32, 34continue from one to the other in apex area 33 where both apex point Sas well as inner surface I are shaped to form an acute angle.

The embodiment of the apex area 43 shown in FIG. 4 represents a furtherexample of a pincette according to the invention where legs 42, 44continue integrally in apex area 43 and are provided with recesses atthe transition to the inner surface, which recesses can be used tocontrol the desired closure pressure of a pincette according to theinvention.

The generally arch-shaped embodiment of apex area 53 illustrated in FIG.5 is shown to have no increased thickness at the transition of legs 52,54 for reasons of explanation. Such an embodiment is usually notpreferred and should (in a manner not shown) be protected againstdeformation of the pincette by a bulge near the lower end of the legs.Such a shape of the upper end of the pincette requires an extrudedlight-metal profile, i.e. must not be formed by bending since that wouldnormally lead to a significant weakening of the grain structure. Incontrast, an extruded profile has a homogeneous grain structure. On theother hand, a suitable extrusion method may lead to an increasedstrength of the grain structure.

FIG. 6 shows a cross-section of an extruded profile 60 with an increasedthickness of up to about 300% (thickness-increase factor 3) at the upperend 61 and with two legs 62, 64 having an increased thickness near lowerends 65, 67 of up to about 200% (thickness-increase factor 2). Thelongitudinal (or axial) extension of extruded profile 60 extendsperpendicular to the plane of drawing while the transverse (or radial)direction extends in the drawing plane.

Extruded profile 60 is a closed profile, i.e. it includes a space 63closed all around. For production of finished pincettes, therefore,lower profile end 69 is closed and requires separation not only bytransverse division (radial plain of division) into a plurality ofpincettes, or green pincettes, respectively, but also requiresseparation in axial direction.

The closed extruded profile 60 presented in FIG. 6 is so shaped at itslower end 69 that division along a plane of division as indicated bydash-dot lines T and extending in axial direction, not only opens theclosed profile but, at the same time, forms a suitable shape of thelower pincette ends 65, 67 which are normally distanced (“opened”) bydistance A, and have gripping areas 651, 671. Upon manual actuation(“closure”) of a pincette according to the invention made from profile60 by transversal or longitudinal division, a wedge-shaped inter-spaceremains which, upon reaching closing pressure, is initially closed butat its lower end, and will be closed progressively only upon anincreasing manual pressure. This is a known feature of conventionalpincettes having a claw-shaped end for achieving a goodgrip-and-hold-effect for an object, e.g. a hair, engaged by thepincette. In conventionally forged pincettes this requires a relativelytime-consuming grinding operation executed by skilled personnel while,according to the invention, a simple separation step is sufficient toachieve this.

When using extruded profile 60 of FIG. 6, angle α of the plane ofdivision indicated by lines T is about 20° degrees but can be variedbetween wide limits, e.g. between 10° and 80°. An angle range between 15and 30° is preferred for many purposes.

According to a preferred embodiment, distance D between bulges 66, 68 inthe lower third of the legs equals distance A at the lower end 69 ofprofile 60, and, consequently, is substantially equal to the distancebetween gripping areas 651, 671 of a pincette produced from the profile60 when at rest, i.e. both gripping areas are distanced from each otherby distance A. Permanent deformation of the pincette upon normal use canessentially be precluded in this manner. A typical pincette made from aprofile of the type shown in FIG. 6 has a total length of about 90 mm, aleg thickness of about 2 mm, a leg width of about 6 mm, a closurepressure of about 200 g and a weight of 2.5 g. A general area ofdimensions is between half and twice the values just mentioned. Aconventionally forged pincette with comparable dimensions has a weightof at least about 6 g, typically about 8–9 g.

Suitable methods for a segmenting division of extruded profiles of alight-metal in axial and radial planes when carrying out the processaccording to the invention are well-known to those experienced in theart. Non-limiting examples of segmenting division techniques aremechanical separation by cutting or sawing as well the use of laserbeams.

Within the context of the invention, metals of typical densities of lessthen about 4 g/ml are understood to be “light-metals”, such as notablyaluminum or magnesium, as well as alloys of such light-metals with eachother and/or with other alloying constituents. The exact composition isnot essential in so far as those experienced in the art of production ofextruded profiles, notably by extrusion under pressure and/or tension,know the required compositions, or are capable of determination thereofin a simple manner. Commercially available alloys consistingpredominantly of Al and/or Mg and generally containing Si and optionalother alloying components can be mentioned by way of example. Examplesof such alloys are light-metal alloys as defined in German IndustrialStandards DIN 1748 under the type designations F11, F21, F28, F31, etc.,as well as alloys obtainable under the trademarks Avional and Perunal.Light-metal alloys which can be electrically oxidized at their surfacesby conventional techniques (“Eloxal-processes”) are preferred for manypurposes.

When compared to conventional forged pincettes made of steel, advantagesof light-metal pincettes according to the invention include not only areduced density and mass as well as an essentially simplified productionprocess using extruded profile material, but also in that surface designof articles made of a light-metal, notably aluminum or aluminum alloys,can be modified in many ways by oxidation techniques feasible therewith,both with regard to coloration possibilities, as well as surfaceproperties (e.g. owing to the hardness of aluminum oxide).

In general, the invention provides a pincette essentially made of alight-metal, predominantly aluminum or aluminum alloys capable ofextrusion, and having one pair of ends and an apex area at the other endfor reversible mutual contact by impact of a manual closure pressure.Preferably, the pincette consists of an extruded light-metal, has amonolithic structure, and provides the essential mechanical propertiesof forged pincettes, namely a sufficiently high closure pressure, a goodgrip-and-hold-effect for objects that can be engaged by a pincette, anda practically any desired resistance against deformation upon normaluse. For pincette manufacture, a preferably closed extruded profile withan approximately pincette-shaped cross-section is used so as to providefor a greatly simplified production.

To those experienced in the art, numerous modifications will be apparentwithin the scope of the invention. This applies, for example, to variousforms of the gripping ends of the pincettes, and the dimensions oflength and width that can be adapted on the basis of the abovedescription. The scope of the invention results from the followingclaims.

1. A tweezer having a longitudinal dimension and comprising first andsecond legs extending along said longitudinal dimension, each leg havinga first end and an opposite second end, the first ends of the legs beingconnected with each other forming an apex area, the second ends of thelegs being unconnected and capable of reversible engagement with eachother upon a manually exerted closure pressure; wherein said tweezersare formed of a light metal profile by extrusion and by separation ofsaid profile approximately transversely to said direction of extrusionof said profile, said tweezer having an essentially monolithicstructure.
 2. The tweezer of claim 1, wherein said closure pressure isat least about 120 g.
 3. The tweezer of claim 2, wherein each of saidfirst and second legs, when viewed in a plane extending transversely tosaid extrusion direction of said profile, has a first thickness; andwherein said apex area, when measured in said plane along saidlongitudinal dimension, has a thickness that is increased by at leastabout 20% above said first thickness of each of said legs.
 4. Thetweezer of claim 3, wherein each of said first and second legs, whenviewed in a plane transverse to said longitudinal dimension of saidtweezer, has an essentially prismatic cross-section, the height of whichcorresponds to said first thickness of said legs, and the width of whichcross-section is at least twice as large as said first thickness.
 5. Thetweezer of claim 2, wherein each of said first and second legs, whenviewed in a plane transverse to said longitudinal dimension of saidtweezer, has an essentially prismatic cross-section, the height of whichcorresponds to a first thickness of said legs, and the width of whichcross-section is at least twice as large as said first thickness.
 6. Thetweezer of claim 1, wherein said closure pressure is at least about 150g.
 7. The tweezer of claim 1, wherein each of said first and secondlegs, when viewed in a plane extending transversely to said extrusiondirection of said profile, has a first thickness; and wherein said apexarea, when measured in said plane along said longitudinal dimension, hasa thickness that is increased by at least about 20% above said firstthickness of each of said legs.
 8. The tweezer of claims 7, wherein eachof said first and second legs has a bulge in which said first thicknessof each of said legs is increased by at least about 30% above said firstthickness of said legs so as to limit deformation of said legs uponmanual compression.
 9. The tweezer of claim 8, wherein each of saidfirst and second legs, when viewed in a plane transverse to saidlongitudinal dimension of said tweezer, has an essentially prismaticcross-section, the height of which corresponds to said first thicknessof said legs, and the width of which cross-section is at least twice aslarge as said first thickness.
 10. The tweezer of claim 1, wherein eachof said first and second legs, when viewed in a plane transverse to saidlongitudinal dimension of said tweezer, has a prismatic cross-section,the height of which corresponds to a first thickness of said legs, andthe width of which cross-section is at least twice as large as saidfirst thickness.
 11. The tweezer of claim 10, wherein said prismaticcross-section is a rectangular cross-section.
 12. The tweezers of claim1, wherein the first and second legs are substantially straight.
 13. Thetweezers of claim 1, wherein the first and second legs contain no acuteangles.
 14. A method of producing a light-metal tweezer having alongitudinal dimension extending from a first end of said tweezer to asecond end thereof, and comprising two legs, each having a first end anda second end, said two legs being interconnected at their first ends inan apex forming said first end of said tweezer; said legs being capableof reversible engagement with each other at their unconnected secondends by a manually exerted closure pressure; said method including thesteps of: providing a light-metal profile produced by extrusion in adirection of extrusion and having, when viewed in a plane transverse tosaid direction of extrusion, a cross-sectional shape at leastapproaching the shape of said tweezer when the latter is viewed in aplane extending through said legs and said apex; and dividing saidprofile by segmenting division approximately transversely to saiddirection of extrusion of said profile to form a plurality oftweezer-shaped elements.
 15. A profile produced by extrusion of a metal,selected from the group consisting of light-metals and light-metalalloys, in a direction of extrusion; said profile when viewed in a planetransverse to said direction of extrusion has a cross-sectional shape atleast approaching that of a monolithic tweezer having a first end and asecond end and comprising two legs, each having a first end and a secondend; said two legs being interconnected at their first ends in an apexforming said first end of said tweezer; said two legs being unconnectedat their second ends forming said second end of said tweezer.